1. Field of the Invention
The present invention relates generally to workpiece authentication techniques, and more specifically, to such techniques which involve imaging one or more portions of the workpiece to generate abstractions (e.g., numeric or alphanumeric strings) which represent random physical characteristics of the surface geometry of the workpiece and/or an optically active medium included on or embedded in the workpiece, and using the abstractions to determine whether the workpiece is authentic.
2. Brief Description of Related Prior Art
A value indicium is a symbol or token that indicates payment for a service. One example of a commonly-used value indicium is the “franking” or postal meter mark, which is placed on a postal mailpiece to indicate that a specified amount of money has been paid to post the mailpiece. Other examples of value indicia include paper currency, money orders, and tickets for cultural events and transportation.
Authentication indicia are symbols or tokens placed on or in a workpiece for use in determining the validity of the workpiece (e.g., whether the workpiece is authentic, as opposed to being a forgery). For example, legal documents, such as passports and driver's licenses often have authentication indicia in the form of validation stamps/seals from a certifying authority (CA), such as the government, placed on them that vouch for the authenticity of the legal documents.
In the past, if a postal franking mark on a postal mailpiece appeared to the ordinary observer (e.g., a postal clerk) to have been made by an authorized postal franking device, the mailpiece would be considered valid and would be posted without further inquiry into whether the mark was genuine. Unfortunately, improvements in photo-copying, computer-based imaging and duplication technologies have rendered this prior art authentication technique unreliable, as they have permitted the unscrupulous to produce high quality forgeries of such franking marks that often appear genuine to the ordinary observer. This has driven interest in creating a postal franking mark whose authenticity can be determined without reference to its appearance, but instead can be determined using different criteria.
In one such conventional validation technique, the franking mark comprises an indicium that contains certain identifying information, such as the postage purchase date, meter identification number, franking sequence number, source and destination addresses of the mailpiece, and a cryptographic signature of the identifying information. According to this technique, mailpiece forgeries are detected based upon whether differences exist between the identifying information and the cryptographic signature in the indicium, and the actual identifying information of the mailpiece and the actual cryptographic signature of such actual identifying information.
Unfortunately, this latter validation technique is unable to thwart certain types of postal franking fraud. For example, if the identifying information and signature of a valid indicium of a first mailpiece are also valid for a second mailpiece, then the indicium of the first mailpiece may be fraudulently copied onto the second mail piece, and the fraudulent copying cannot be detected using this technique. Hereinafter, this type of fraud will be termed “double spending fraud.”
Additionally, advances in networking technology have also permitted wide access to the data underlying such franking marks. For example, one could download such data using the Internet from a computer node storing such data (e.g., via email or a World Wide Web posting), and depending upon the manner in which this conventional technique is implemented, a large number of seemingly valid franking marks could be generated based upon such data. This further exacerbates the possibility and opportunity for such fraud.
In one prior art technique that is used to try to thwart double spending fraud, a database tracks use of value indicia and the respective identifying information therein. If two mailpieces have identical indicia, the database indicates this as a possible occurrence of double spending fraud.
Unfortunately, in practical implementation, this conventional double spending fraud detection technique requires use of a large database to track the indicia's identifying information. Disadvantageously, the burden and expense of maintaining and querying such a large database is undesirable. Also disadvantageously, this conventional fraud detection technique does not permit off-line verification of the indicia (i.e., not based upon information obtained via a network), and no mechanism is provided in this technique to determine which indicium among indicia determined to be identical is authentic.
Another prior art fraud problem arises when unauthorized use is made of data or digital tokens (e.g., stored in a computerized postal franking system's internal memory) that when supplied to the system cause it to produce otherwise valid authentication indicia.
One solution to the problems discussed above is to produce an authentication indicium that corresponds to a string that is based upon, at least in part, intrinsic physical characteristics of a designated portion of the workpiece. The physical characteristics include one or more images of surface topographical appearance produced by illuminating the designated portion of the workpiece. A system and method for producing such authentication indicia is discussed in U.S. patent application Ser. No. 09/719,430 filed Dec. 12, 2000 entitled WORKPIECE AUTHENTICATION BASED UPON ONE OR MORE WORKPIECE IMAGES, which is incorporated herein by reference. Basically, a reader illuminates the designated portion of the workpiece, to produce one or more images that consist of patterns that are the result of light that is reflected by features of the surface geometry of the designated portion of the workpiece. The images are sometimes referred to herein as “enrollment images.” The reader then produces a signal that corresponds to the enrollment images, and incorporates the signal into the string on which the authentication indicium is based. The signal may correspond to the appearance of the surface features, i.e., a two dimensional representation, or when different lighting conditions are used for the various enrollment images, to implicitly defined three dimensional surface features.
To verify the authenticity of the workpiece, the system thereafter illuminates the designated portion and produces one or more new images, which are sometimes referred to herein as “verification images.” The system may then generate a corresponding string and/or indicium and compare the result with the string and/or indicium that is associated with the workpiece. Alternatively, the system may compare the verification images with the enrollment images, which may be reproduced from the information contained in the indicium.
When the enrollment images are produced the workpiece is in a particular position with respect to the illumination sources and the camera that are included in the reader. The arrangement of the workpiece, illumination sources and camera is referred to hereinafter as the “enrollment geometry,” and the images necessarily depend on the particular enrollment geometry.
The workpiece includes registration information, such as an arrangement or constellation of dots in predetermined locations on the workpiece. Using the registration information, the system determines that the workpiece is in the desired position with respect to the components of the reader during the enrollment operations.
During verification operations, the system must also ensure that the verification images are produced using a “verification geometry” that is essentially the same as the enrollment geometry. The system may thus use the registration information included on the workpiece to mechanically reposition the workpiece such that the verification geometry is physically the same as the enrollment geometry. Alternatively, the system may use the registration information to determine coordinate axes in the images and/or which pixels to sample and thus computationally match the verification geometry to the enrollment geometry essentially, as long as the workpiece is in a relatively similar position and/or orientation.
The two authentication systems discussed above work well to correctly identify as genuine or counterfeit a workpiece that is in a position that is sufficiently close to reproduce the enrollment geometry. The relatively strict registration requirement may, however, limit the types of readers that can be used and/or present an obstacle to an inexperienced user. For example, if a stationary reader, similar to a bar code reader, is used, the user must not only place the workpiece in the proper orientation and position, the user must also ensure that surface of the designated portion of the workpiece is parallel to the reader. As discussed above, the workpiece may be the paper on which a document, a postal franking mark or currency is printed, a label that is secured to an object after the indicia is printed thereon, or an object, and thus, the re-positioning of the workpiece to match the enrollment geometry relative to, for example, a handheld reader or even a stationary stand-alone reader may be time consuming and/or frustrating. Thus, a system that relaxes the verification registration requirement is desired.